JP6066213B2 - Secondary battery manufacturing method and secondary battery - Google Patents

Description

  The present invention relates to a secondary battery manufacturing method and a secondary battery that perform a step of injecting an electrolytic solution into a decompressed battery case.

Conventionally, in a manufacturing process of a secondary battery such as a lithium ion secondary battery, a wound body formed by winding a positive electrode, a negative electrode, and a separator is housed in the exterior in a lateral orientation.
In the manufacturing process of the secondary battery, after the electrolyte solution is injected into the exterior, the battery container is sealed, and the electrolyte solution is infiltrated into the wound body. And in the manufacturing process of a secondary battery, initial charge is performed with respect to a secondary battery. At this time, a film is formed on the wound body by the decomposition reaction of the electrolytic solution.

In the technique disclosed in Patent Document 1, an opening of a case (battery case) is closed to decompress the inside of the case, and an electrolytic solution is injected into the decompressed case.
In the technique disclosed in Patent Document 1, while injecting an electrolyte solution (or simultaneously with the injection of the electrolyte solution), the pressure in the case is increased to a pressure higher than the atmospheric pressure, and the electrolyte solution is wound. To penetrate.

Immediately after the injection, the electrolytic solution penetrates into both axial ends of the wound body by capillary action. Thereby, a sealed space is formed inside the wound body.
When the pressure in the case is increased while injecting the electrolyte solution as in the technique disclosed in Patent Document 1, the air in the pressurized case penetrates into both axial ends of the wound body. The electrolyte may be pushed away and air may enter the wound body.
That is, in this case, there is a possibility that the electrolytic solution cannot penetrate into the air intrusion path and the axially central portion of the wound body.

  For this reason, with the technique disclosed in Patent Document 1, there is a possibility that a uniform film cannot be formed on the wound body.

JP-A-9-102443

  The present invention has been made in view of the above situation, and provides a method for manufacturing a secondary battery and a secondary battery that can form a uniform film on a wound body.

A method for manufacturing a secondary battery according to the present embodiment is a method for manufacturing a sealed secondary battery including a battery case, a wound body, and an electrolyte solution, and a winding axis direction with respect to a lower surface of the battery case A step of decompressing the inside of the battery case in a state where the wound body is accommodated so as to be parallel to each other, and an electrolytic solution in which an additive capable of generating a gas by a decomposition reaction is added to the decompressed battery case A step of sealing the battery case into which the electrolytic solution has been injected, a wound body external space that is a space between the sealed battery case and the wound body, and the wound body Waiting to reduce the differential pressure with the internal space, allowing the electrolytic solution to permeate from both axial ends of the wound body to reduce the volume of the wound body internal space, and the wound body Initially charging a secondary battery infiltrated with the electrolyte solution; A step of performing high temperature aging on the initially charged secondary battery while maintaining sealing of the case, and the step of performing high temperature aging on the electrolyte by generation of gas due to decomposition reaction of the additive. An additive is added in such an amount that the pressure in the battery case when it is performed is higher than the saturated vapor pressure during high-temperature aging of the electrolyte.

  In the method of manufacturing a secondary battery according to the present embodiment, the pressure in the battery case when the high temperature aging process is performed on the electrolytic solution due to the generation of the gas is The amount of the additive is adjusted so as to be higher than the saturated vapor pressure, and the amount of the additive in which the pressure in the battery case is lower than the saturated vapor pressure during high-temperature aging of the electrolytic solution in the initial charging step. It is what is added.

  In the method for manufacturing a secondary battery according to the present embodiment, the electrolyte is added in such an amount that the pressure in the battery case at the end of the initial charging is approximately equal to the atmospheric pressure due to the generation of the gas. Things are added.

  In the method of manufacturing a secondary battery according to the present embodiment, in the initial charging step, the secondary battery is charged at a lower rate in the potential region where the gas is generated than in other potential regions.

Secondary battery according to this embodiment includes a battery case, and the wound body prior Symbol Kaijiku direction winding the lower surface of the battery case a wound body which is housed in the battery case are parallel, electrolytic a liquid, a secondary battery sealed equipped with. Then, before Symbol electrolyte, additives capable of generating gas by decomposition reactions are added, the addition amount of the additives, the following conditions:
By the generation of gas due to the decomposition reaction of the additive, sealed pressure in the battery case when performing Atsushi Ko aging is higher on the saturated vapor pressure at high temperature aging of the electrolyte;
It is the quantity which satisfy | fills .

  The present invention has an effect that a uniform film can be formed on a wound body.

Explanatory drawing which shows the whole structure of a battery. Explanatory drawing which shows a mode that a winding body is manufactured. (A) The figure which shows a mode that a positive electrode, a negative electrode, and a separator are wound. (B) The figure which shows a mode that press processing is performed to the winding body. Explanatory drawing which shows the mode from the pressure reduction process of this embodiment to a sealing process. Explanatory drawing which shows an injection unit. Explanatory drawing which shows a mode that a liquid injection unit is operated. (A) The figure which shows the mode at the time of a pressure reduction process. (B) The figure which shows the mode at the time of a liquid injection process. Explanatory drawing which shows the osmosis | permeation degree of the electrolyte solution at the time of a liquid injection process. (A) Sectional drawing. (B) The perspective view of a winding body. Explanatory drawing which shows the mode from the infiltration process of this embodiment to a high temperature aging process. Explanatory drawing which shows the penetration | invasion degree of the electrolyte solution at the time of a osmosis | permeation process. (A) Sectional drawing. (B) The perspective view of a winding body. Explanatory drawing which shows the osmosis | permeation degree of the electrolyte solution at the time of an initial stage charge process. (A) Sectional drawing. (B) The perspective view of a winding body. Explanatory drawing which shows the osmosis | permeation degree of the electrolyte solution after an initial stage charge process. (A) Sectional drawing. (B) The perspective view of a winding body. The figure which shows the result of having changed the additive and evaluating the film. With respect to a battery using LPFO as an additive to the electrolytic solution and a battery using LiBOB as an additive to the electrolytic solution, the aging of the pressure in the exterior from the injection of the electrolytic solution into the exterior to the end of high-temperature aging The figure which shows a change.

  Below, the manufacturing method (henceforth a "manufacturing method") of the sealed battery of this embodiment is demonstrated.

  First, a schematic configuration of a battery which is an embodiment of a secondary battery according to the present invention will be described.

  The battery 10 of this embodiment is a sealed lithium ion secondary battery. The target to which the present invention is applied is not limited to the lithium ion secondary battery, but can be applied to other secondary batteries such as a nickel metal hydride secondary battery.

  As shown in FIG. 1, the battery 10 includes a power generation element 20, an exterior 30, a cap 40, and external terminals 50 and 50.

  The power generation element 20 is obtained by infiltrating an electrolyte E into a wound body 100 formed by winding a positive electrode 101, a negative electrode 102, and a separator 103 (see FIGS. 2 and 3). When the battery 10 is charged / discharged, a chemical reaction occurs in the power generation element 20 (strictly speaking, ion movement occurs between the positive electrode 101 and the negative electrode 102 via the electrolytic solution E), thereby generating a current flow. .

  The exterior 30 that is a battery case is a prismatic can that is formed in a substantially rectangular shape in plan view with the left-right direction in FIG. 1 as the longitudinal direction. The exterior 30 has a storage part 31 and a lid part 32.

  The storage unit 31 is a bottomed rectangular tube-shaped member whose bottom surface and side surfaces are closed and whose top surface is open, and stores the power generation element 20 therein.

  The lid portion 32 is a flat member having a shape corresponding to the opening surface of the storage portion 31 and is joined to the storage portion 31 in a state where the opening surface of the storage portion 31 is closed. In the lid portion 32, a liquid injection hole 33 for injecting the electrolytic solution E is formed between locations where the external terminals 50 and 50 are inserted as will be described later.

  The liquid injection hole 33 is a hole penetrating the plate surface of the lid portion 32, that is, a hole formed in the upper surface of the exterior 30. The liquid injection hole 33 is a substantially circular hole in a plan view having different inner diameters on the upper side (outer side) and the lower side (inner side) of the lid portion 32. The liquid injection hole 33 is formed such that the upper inner diameter is larger than the lower inner diameter, and a step portion is formed in the middle of the upper and lower sides.

The cap 40 is a lid that seals the liquid injection hole 33. The outer diameter of the cap 40 is substantially the same as the inner diameter on the upper side of the liquid injection hole 33.
The cap 40 is placed on the step portion of the liquid injection hole 33 and joined to the lid portion 32 by laser welding of the outer peripheral edge portion.

The external terminals 50 and 50 are arranged in a state in which part of the external terminals 50 and 50 protrudes upward (outward) of the battery 10 from the outer surface of the lid portion 32. The external terminals 50 and 50 are electrically connected to the positive electrode 101 or the negative electrode 102 of the power generation element 20 through current collecting terminals 51 and 51. The external terminals 50 and 50 are fixed to the lid portion 32 in an insulated state with the insulating members 52 and 53 interposed therebetween by fitting the fixing member 34 on the outer peripheral surface portion thereof. The external terminals 50 and 50 and the current collecting terminals 51 and 51 function as an energization path for taking out the electric power stored in the power generation element 20 to the outside or taking in electric power from the outside into the power generation element 20.
The current collecting terminals 51 and 51 are connected to the positive electrode plate and the negative electrode plate of the power generation element 20. As the material of the current collecting terminals 51 and 51, for example, aluminum can be used on the positive electrode side and copper on the negative electrode side.

The external terminals 50 and 50 are threaded by thread rolling at portions protruding outward of the battery 10 to form bolt portions. When the battery 10 is actually used, a bus bar, a connection terminal of an external device, and the like are fastened and fixed to the external terminals 50 and 50 using the bolt portion.
When fastening and fastening, a fastening torque is applied to the external terminals 50 and 50, and an external force is applied in the axial direction by screw fastening. For this reason, it is preferable to employ a high-strength material such as iron as the material of the external terminals 50 and 50.

  Next, the manufacturing method of this embodiment is demonstrated.

First, in the manufacturing method, a mixture (a positive electrode mixture and a negative electrode mixture) is applied to the surface of a current collector (a positive electrode current collector and a negative electrode current collector) using a coating machine such as a die coder. Allow the agent to dry.
Next, in the manufacturing method, a mixture layer (a positive electrode mixture layer and a negative electrode mixture layer) is formed on the surface of the current collector by pressing the mixture on the surface of the current collector. A positive electrode 101 and a negative electrode 102 are generated.

As shown in FIG. 2, in the manufacturing method, the separator 103 is sandwiched between the positive electrode 101 and the negative electrode 102 and stacked.
In the manufacturing method, winding is performed by winding the separator 103 between the positive electrode 101 and the negative electrode 102 with the axial direction of the positive electrode 101 as the winding axis direction, and pressing the outer peripheral surface of the wound one. 100 is generated (see arrow shown in FIG. 2).

  In the manufacturing method, the external terminals 50 and 50 and the current collecting terminals 51 and 51 integrated with the lid portion 32 of the exterior 30 are connected to the wound body 100, and the wound body 100 is connected to the storage portion 31 of the exterior 30. Storing. Thereafter, in the manufacturing method, the storage portion 31 and the lid portion 32 of the exterior 30 are joined and sealed by welding.

At this time, as shown in FIG. 2 and FIG. 3, in the manufacturing method, the winding body 100 is in a lateral orientation, that is, the axial direction of the winding body 100 (the winding axis direction) is relative to the longitudinal direction of the exterior 30. The wound body 100 is housed in the exterior 30 so as to be parallel to each other.
That is, in FIG. 3, the axial direction of the wound body 100 is the left-right direction.

Hereinafter, an internal space of the wound body 100, that is, a space formed between the stacked surfaces of the positive electrode 101, the negative electrode 102, and the separator 103 is referred to as a “winding body internal space S1”.
In addition, a space between the exterior 30 and the wound body 100, that is, a space obtained by removing the wound body internal space S <b> 1 from the internal space of the exterior 30 is referred to as “winding body external space S”.

As shown in FIG. 3, after sealing the exterior 30, in the manufacturing method, the air in the exterior 30 disposed in an atmospheric atmosphere of 1 atm is discharged from the liquid injection hole 33 to reduce the pressure in the exterior 30. A decompression step is performed (see an upward arrow A shown in FIG. 3).
At this time, in the manufacturing method, the inside of the exterior 30 is decompressed until a high degree of vacuum is obtained. The air in the wound body internal space S1 passes through both end portions 100a and 100b in the axial direction of the wound body 100 and exits to the wound body outer space S, and is then discharged to the outside.

  After reducing the pressure inside the exterior 30, in the manufacturing method, a liquid injection step of injecting the electrolytic solution E into the external pressure 30 from the liquid injection hole 33 is performed (see arrow E shown in FIG. 3).

  Such a pressure reduction process and a liquid injection process are performed using the liquid injection unit 110 as shown in FIG. 4, for example.

As shown in FIG. 4, the liquid injection unit 110 includes a liquid injection pod 111 in which an electrolytic solution E is stored, connected to the upper port of the three-way valve 112, and a vacuum pump connected to the left port of the three-way valve 112. Is connected to.
The liquid injection unit 110 is disposed above the exterior 30 and is configured to be movable in the vertical direction, that is, to be able to move up and down. In FIG. 4, the other port is not connected to the lower port of the three-way valve 112.

As shown in FIG. 5A, in the manufacturing method, when the pressure reducing process is performed, the liquid injection unit 110 is lowered to bring the three-way valve 112 and the step portion of the liquid injection hole 33 into contact with each other, thereby injecting the liquid injection hole 33. And the exterior 30 is connected to the lower port of the three-way valve 112.
In the manufacturing method, the three-way valve 112 is controlled to connect the exterior 30 and the vacuum pump, and the vacuum pump is driven to decompress the interior of the exterior 30.

  As shown in FIG. 5 (b), after the exterior 30 is depressurized, in the manufacturing method, the three-way valve 112 is controlled so that the exterior 30 and the liquid injection pod 111 communicate with each other. The electrolytic solution E is injected into the exterior 30 using a pressure difference from the above pressure.

At this time, as shown in FIG. 6, the electrolyte E penetrates vigorously into the axial end portions 100 a and 100 b of the wound body 100 immediately after the injection due to capillary action (see arrows shown in FIG. 6).
As a result, the electrolyte solution E permeates the axial end portions 100a and 100b of the wound body 100, and the electrolyte solution E fills the space formed between the stacked surfaces of the positive electrode 101, the negative electrode 102, and the separator 103. It is done.

That is, the wound body internal space S1 is isolated from the wound body external space S by the electrolytic solution E immediately after the injection, and becomes a sealed space.
When the wound body inner space S1 becomes a sealed space, the wound body outer space S and the wound body inner space S1 are spaces whose pressure is sufficiently lower than the atmospheric pressure, that is, a vacuum layer.

In the manufacturing method of the present embodiment, a solution obtained by adding an additive to a solution obtained by dissolving a lithium salt in an organic solvent or the like is used as the electrolytic solution E.
Examples of the lithium salt include LiPF6 (lithium hexafluorophosphate).
Examples of the organic solvent include ethylene carbonate.

In the manufacturing method of this embodiment, the substance shown in the following structural formula is added as an additive.

  In the following, the substance represented by the structural formula 1 is referred to as “additive LPFO”.

  Thus, in the manufacturing method of the present embodiment, the electrolytic solution E to which the additive LPFO has been added in the liquid injection step is injected into the exterior 30.

As shown in FIG. 3, after injecting the electrolyte E into the exterior 30, the manufacturing method returns the interior of the exterior 30 to atmospheric pressure (1 atmosphere in the present embodiment) (downward arrow A shown in FIG. 3). reference).
At this time, in the manufacturing method, the liquid injection unit 110 is raised from the state shown in FIG. Thereby, in the manufacturing method, the wound body outer space S is returned to atmospheric pressure.

The differential pressure between the wound body outer space S and the wound body inner space S1 returned to the atmospheric pressure is about 1 atm at most, that is, small.
Therefore, the air introduced into the exterior 30 (winding body outer space S) when the atmosphere is released cannot push out the electrolytic solution E that has permeated the axial end portions 100a and 100b of the winding body 100.

  For this reason, the wound body inner space S1 remains isolated from the wound body outer space S even after the exterior 30 is opened to the atmosphere, that is, in a state where the wound body is decompressed (a vacuum layer is formed). State).

In the manufacturing method, the pressure of the wound body external space is adjusted so that the wound body internal space can be kept isolated from the wound body external space even after the liquid injection process. It is not necessary to return the outer space of the wound body to atmospheric pressure after the liquid injection process.
For example, the manufacturing method may pressurize the inner space of the wound body to a pressure higher by several Pa than atmospheric pressure or a pressure lower by several Pa after the liquid injection process.

After the interior of the exterior 30 is returned to atmospheric pressure, in the manufacturing method, the cap 40 is placed in the liquid injection hole 33, and laser is irradiated along the outer edge of the cap 40 by a laser welding machine. Is sealed (see the black triangle shown in FIG. 3).
Thus, in the manufacturing method, the cap 40 is welded to the liquid injection hole 33, the liquid injection hole 33 is fully sealed by the cap 40, and the sealing process for sealing the exterior 30 in which the electrolytic solution E is injected is performed.

  Thereby, the wound body external space S becomes a sealed space. At this time, the pressure in the wound body outer space S is atmospheric pressure.

  As shown in FIG. 7, after the sealing process is performed, in the manufacturing method, the exterior 30 is left for a certain period of time to perform a permeation process in which the electrolytic solution E penetrates into the wound body 100 (the exterior shown in the upper left of FIG. 7). 30).

In the manufacturing method, air enters the exterior 30 from the outside during the permeation process by performing a sealing process before the permeation process (after the electrolyte E has permeated the axial ends 100a and 100b of the wound body 100). To prevent it.
Thereby, the manufacturing method can suppress the fall of the battery performance resulting from the evaporation of the electrolyte solution E and the influence of the water | moisture content and oxygen contained in air.

  When performing the sealing step and the infiltration step, the pressure in the wound body outer space S is atmospheric pressure. On the other hand, the pressure in the winding body internal space S1 is a high degree of vacuum, that is, a pressure close to vacuum.

That is, in the manufacturing method, the sealing step and the infiltration step are performed in a state where the pressure in the wound body outer space S is higher than the pressure in the wound body inner space S1.
Thereby, as shown in FIG. 8, in the manufacturing method, the electrolytic solution E is infiltrated into the wound body 100 so as to fill the differential pressure between the wound body outer space S and the wound body inner space S1.

Specifically, since the height position of the liquid surface of the electrolytic solution E is lowered as the electrolytic solution E penetrates, the volume of the wound body outer space S is increased.
Therefore, the pressure in the wound body outer space S after the sealing step becomes lower as the electrolyte E penetrates.

The electrolyte E penetrates from the axial end portions 100a and 100b toward the axial center portion 100c, and the winding body internal space S1 (vacuum layer) is directed toward the axial center portion 100c of the winding body 100. Move (see arrow shown in FIG. 8A).
Therefore, the volume of the wound body internal space S1 decreases as the electrolyte E penetrates. For this reason, the pressure in the winding body internal space S1 increases as the electrolyte E penetrates.

  That is, in the manufacturing method, the pressure in the wound body outer space S, where the pressure decreases as the electrolyte solution E penetrates, is greater than the pressure in the wound body internal space S1, where the pressure increases as the electrolyte solution E penetrates. By making it high, the differential pressure between the wound body outer space S and the wound body inner space S1 is reduced by the permeation of the electrolytic solution E.

According to this, the manufacturing method can make the electrolyte solution E permeate | transmit the winding body 100 effectively using the differential pressure | voltage of the winding body outer space S and the winding body internal space S1.
Therefore, the manufacturing method can promote the penetration of the electrolytic solution E into the wound body 100.

Thus, in the permeation step, while maintaining the sealed state of the exterior 30 and waiting to reduce the differential pressure between the wound body outer space S of the sealed exterior 30 and the wound body inner space S1, The electrolytic solution E is infiltrated from both ends 100a and 100b in the axial direction of the wound body 100 to reduce the volume of the wound body internal space S1.
Further, the wound body 100 is left after the sealing step, so that the electrolyte E penetrates from both axial ends 100a and 100b, and the volume of the wound body internal space S1 is reduced.

The electrolytic solution E penetrates the wound body 100 at a higher speed as the differential pressure between the wound body outer space S and the wound body inner space S1 is larger. For this reason, the electrolyte solution E penetrates the wound body 100 vigorously immediately after the sealing step.
As the electrolytic solution E penetrates, the differential pressure between the wound body outer space S and the wound body inner space S1 becomes smaller, so that the speed of the electrolyte E penetrating into the wound body 100 with time elapses. Become.
The electrolyte E stops permeating the wound body 100 when the pressures in the wound body outer space S and the wound body inner space S1 are balanced (when balanced).

Therefore, in the infiltration process of the present embodiment, the process waits until the pressures in the wound body outer space S and the wound body inner space S1 are balanced.
The waiting time in such an infiltration step is, for example, measuring the pressure in the exterior 30, that is, the pressure in the wound body outer space S with a commercially available pressure sensor, and evaluating the time until the measurement result of the pressure sensor becomes constant. It is set as appropriate based on the results.

  Here, the wound body 100 is in a state where a slight gap is formed between both side surfaces in the thickness direction and both side surfaces in the short direction of the storage unit 31 or in the short direction of both side surfaces in the thickness direction and the storage unit 31. It is accommodated in the exterior 30 in a state where both side surfaces are in close contact.

Therefore, in the state before the wound body outer space S is injected with the electrolytic solution E, the space on both the upper and lower sides and the left and right sides of the wound body 100 occupies most of the volume.
Further, when the electrolytic solution E is injected into the exterior 30, the volume of the wound body outer space S is reduced to, for example, about half.

That is, since the volume of the wound body outer space S is small at the time of starting the permeation process, the pressure tends to decrease with the permeation of the electrolytic solution E.
Accordingly, even when waiting for the pressure in the wound body outer space S and the wound body inner space S1 to be balanced, the electrolyte E does not penetrate to the axially central portion 100c of the wound body 100.

  As shown in FIG. 7 and FIG. 9, after the infiltration step is performed, in the manufacturing method, an initial charging step for initially charging the battery 10 in which the electrolytic solution E is infiltrated into the wound body 100 is performed.

At this time, in the manufacturing method, while maintaining the sealed state of the exterior 30, the exterior 30 is restrained by a restraining jig, and is predetermined with respect to the exterior 30 along the thickness direction of the exterior 30 (the depth direction in FIG. 7). The load of the magnitude | size of is given.
And in a manufacturing method, the electrode of the power supply device 120 is connected to the external terminals 50 and 50, and the battery 10 is initially charged.

  Thereby, in the wound body 100, the additive LPFO (electrolytic solution E) causes a decomposition reaction at a portion where the electrolytic solution E penetrates, and a film is formed at a portion where the electrolytic solution E penetrates.

  At this time, the wound body 100 is formed with a film from both axial end portions 100a and 100b (see arrows shown in white in FIG. 9).

Further, in the portion of the wound body 100 where the film is formed, gas G is generated by the decomposition reaction of the additive LPFO (electrolytic solution E) excluding the decomposition reaction for film formation.
That is, in the initial charging step, gas G is generated outside the wound body internal space S1.

  Thus, in the manufacturing method, by adding the additive LPFO to the electrolytic solution E, the gas G is intentionally generated at the time of film formation, and the wound body inner space S1 and the outer space (more specifically, A differential pressure is generated between the wound body 100 and the portion on which the film is formed.

  For this reason, in the manufacturing method, the electrolytic solution E can be infiltrated into the wound body 100 even when the initial charging step is performed (see the arrow shown in the vicinity of the axial center portion 100c of the wound body 100 in FIG. 9). .

Specifically, when the gas G is generated in a portion of the wound body 100 where the electrolytic solution E located outside the wound body internal space S1 is permeated, bubbles are formed and remain there. Due to the bubbles remaining in the portion where the electrolytic solution E has permeated, the electrolytic solution E is pushed out toward the axially central portion 100c of the wound body 100 and the outside of the wound body 100.
As a result, the electrolytic solution E penetrates into the axially central portion 100c of the wound body 100. In addition, the electrolyte E pushed out of the wound body 100 is outside the wound body in which the pressure generated by the air bubbles generated from the electrolyte E existing outside the wound body 100 is higher than that of the wound body internal space S1. It is pushed into the wound body 100 again by the pressure in the space S.
Thus, in the initial charging step, the electrolytic solution E is infiltrated into the wound body 100 by the generated gas G.

  Therefore, in the manufacturing method, the electrolytic solution E can be further permeated toward the axially central portion 100c of the wound body 100, and the wound body internal space S1 (vacuum layer) can be formed in the axial direction of the wound body 100. The center portion 100c can be compressed (see the arrow in the vicinity of the central portion 100c in the axial direction in FIG. 9).

  That is, in the manufacturing method, in the initial charging process, a film is formed on the portion where the electrolyte solution E is infiltrated in the infiltration process of the wound body 100, and the gas G generated during the film formation is used to infiltrate in the infiltration process. The electrolyte solution E is infiltrated into the portion that could not be obtained (see the arrow shown in FIG. 9).

Thereby, as shown in FIG. 10, the manufacturing method can permeate | transmit the electrolyte solution E to the axial direction center part 100c of the winding body 100 during an initial stage charging process. That is, in the manufacturing method, the electrolytic solution E can penetrate the entire surface of the wound body 100.
In addition, the manufacturing method includes forming a film on a portion where the electrolytic solution E can be permeated in the permeation step (a portion excluding the central portion 100c in the axial direction of the wound body 100), and then applying the electrolytic solution E during the initial charging step. A film can be formed on the portion (the axially central portion 100c) that could be permeated.

According to this, a manufacturing method can form a membrane | film | coat sequentially from the axial direction both ends 100a * 100b of the winding body 100 toward the axial direction center part 100c. Moreover, the manufacturing method can prevent the electrolyte solution E and an active material from contacting more than necessary (after film formation) by intentionally generating gas G in the part in which the film was formed.
Therefore, the manufacturing method can prevent the film from being excessively formed in the portion where the electrolytic solution E could be permeated in the permeation step.

That is, the manufacturing method can form a uniform film on the entire surface of the wound body 100.
For this reason, in the manufacturing method, the battery 10 capable of maximizing the potential can be manufactured.

Moreover, the manufacturing method can compress the axial direction center part 100c, ie, a vacuum layer, by making electrolyte solution E permeate | transmit the axial direction center part 100c of the winding body 100 at the time of an initial charging process.
Therefore, the manufacturing method can manufacture the battery 10 with good heat dissipation.

Here, the electrolytic solution E penetrates the central portion 100c in the axial direction of the wound body 100 by the same amount as the gas G is generated, that is, by the same amount as the volume of the gas G.
For example, when about 3 cc of gas G is generated during the initial charging step, the electrolyte E penetrates the axially central portion 100c of the wound body 100 by about 3 cc.

Therefore, in the manufacturing method, the additive LPFO whose amount is adjusted so that the gas G is generated in an amount equivalent to the volume of the wound body internal space S1 after the volume is reduced during the initial charging step is used as the electrolytic solution. E is added.
Further, the amount of the additive LPFO added to the electrolytic solution E can be set to such an amount that the pressure in the exterior 30 at the end of the initial charging becomes approximately the same as the atmospheric pressure due to the generation of the gas G at the initial charging.

  Thereby, the manufacturing method can suppress the quantity of the gas G generated at the time of an initial charge process, and can suppress that the pressure in the exterior 30 becomes higher than necessary.

  Therefore, the manufacturing method can form a uniform film on the entire surface of the wound body 100 and can manufacture the battery 10 without degassing in a later step.

In the manufacturing method, it is preferable that most of the air in the winding body inner space is discharged to the outside during the decompression step.
Thereby, since the manufacturing method can make more electrolyte solution osmose | permeate a winding body at an osmosis | permeation process, it can reduce the quantity of the gas deliberately generated at the time of an initial charge process. Therefore, the manufacturing method can reliably prevent the pressure in the exterior from increasing during the initial charging step.

In the infiltration step, it is not always necessary to wait until the pressures in the wound body outer space and the wound body inner space are balanced.
The manufacturing method of this embodiment waits until the pressure of the wound body outer space S and the wound body inner space S1 is in equilibrium, thereby reducing the volume of the wound body inner space S1 before the pressurizing step. doing.
Thereby, since the manufacturing method can make more electrolyte solution osmose | permeate a winding body at an osmosis | permeation process, it can reduce the quantity of the gas deliberately generated at the time of an initial charge process.

After performing the initial charging step, in the manufacturing method, a high temperature aging step of performing high temperature aging on the exterior 30 (battery 10) is performed. The high-temperature aging step is a step of leaving the exterior 30 for a certain period of time in a high-temperature environment while maintaining the sealed state of the exterior 30 while the exterior 30 is being restrained by a restraining tool that restrains the exterior 30 during the initial charging step. It is.
Thereby, in the manufacturing method, the discharge characteristics of the secondary battery 10 are stabilized.

After performing the high temperature aging process, in the manufacturing method, the voltage is inspected and the restraint of the exterior 30 by the restraining jig is released.
In the manufacturing method, the battery 10 is manufactured in this way.

  As described above, when the battery 10 is initially charged, the electrolytic solution E of the battery 10 decomposes the additive LPFO by an amount similar to the volume of the wound body internal space S1 after the volume is reduced. The additive LPFO whose amount is adjusted so as to generate the gas G is added.

Here, in the manufacturing method, due to the shape of the wound body 100, for example, the length and thickness (the number of windings) in the axial direction, there is not enough time to form a film only at the time of the initial charging process. There is a possibility that the gas G cannot be generated during the initial charging step by an amount equivalent to the volume of the wound body internal space S1.
In this case, a film is continuously formed during the high temperature aging process. Accordingly, in this case, in the manufacturing method, the remaining gas G is generated during the high temperature aging process.
That is, in this case, the electrolytic solution E penetrates to the axial center part 100c of the wound body 100 during the high temperature aging process, and then a film is formed on the axial center part 100c of the wound body 100. .

  Specifically, the penetration of the electrolytic solution E is caused by the winding body outer space S whose volume is expanded by the high temperature aging process and the gas G bubbles existing in the winding body outer space S This is done by pushing into the central part 100c in the axial direction of the wound body 100. In this case, since the bubbles dissolved in the electrolytic solution E go out to the outside due to the temperature rise of the battery 10, the electrolytic solution E effectively permeates the axially central portion 100c of the wound body 100. Will be.

As described above, in the high temperature aging process, the exterior 30 is left in a high temperature environment. For this reason, the exterior 30 is heated to a constant temperature during the high temperature aging process.
Therefore, in the high temperature aging process, the pressure inside the wound body outer space S and the wound body inner space S1, that is, the exterior 30 increases.

  In the manufacturing method of the present embodiment, the amount of additive LPFO, that is, the amount of gas G generated in the initial charging step, is adjusted so that the pressure in the outer package 30 is equal to or higher than the saturated vapor pressure of the electrolyte E during the high temperature aging step. It is adjusted. As described above, the additive LPFO is added to the electrolytic solution E by the generation of the gas G so that the pressure in the exterior 30 during the high temperature aging process becomes higher than the saturated vapor pressure during the high temperature aging of the electrolytic solution E. Has been.

According to this, the manufacturing method can prevent the electrolyte solution E from volatilizing during the high temperature aging process.
Therefore, the manufacturing method can prevent the electrolytic solution E volatilized during the high temperature aging process from filling the axially central portion 100c of the wound body 100. That is, the manufacturing method can prevent the volatilized electrolytic solution E from inhibiting the penetration of the liquid electrolytic solution E into the wound body 100.

For this reason, in the manufacturing method, the electrolytic solution E can be permeated into the axially central portion 100c of the wound body 100 even in the high temperature aging process, and a film can be formed on the axially central portion 100c of the wound body 100.
Therefore, the manufacturing method can reliably form a uniform film on the wound body 100 regardless of the shape of the wound body 100.

  Further, in the manufacturing method, the amount of additive LPFO added to the electrolytic solution E, that is, the amount of gas G generated is adjusted, and the pressure in the exterior 30 is adjusted to the level of the electrolytic solution E before the high temperature aging process (immediately after the initial charging process). It is designed to be lower than the saturated vapor pressure.

  Thereby, since the manufacturing method can prevent the pressure in the exterior 30 from becoming higher than necessary, the battery 10 can be manufactured without degassing in a later step.

As described above, in the electrolytic solution E, due to the generation of the gas G, the pressure in the exterior 30 becomes higher than the saturated vapor pressure of the electrolytic solution E during the high temperature aging process, and the pressure in the exterior 30 immediately after the initial charging process is increased. The additive LPFO whose amount is adjusted so as to be lower than the saturated vapor pressure of the electrolytic solution E is added.
The amount of such additive LPFO is appropriately set based on the conditions for high-temperature aging (temperature for heating the exterior 30), the pressure in the exterior 30 immediately after the initial charging step, and the like.

  Here, the gas G generated during the initial charging process is generated in a certain potential region. The film formation rate increases as the charge rate during the initial charging step increases.

Therefore, in the initial charging step of the manufacturing method, the battery 10 is charged by flowing a lower current in the potential region where the gas G is generated than the other potential regions, that is, by passing a low current through the battery 10.
That is, in the manufacturing method, the initial charging process is not performed at a constant rate, but the initial charging process is performed with the potential region where the gas G is generated at a low rate and the other potential regions at a higher rate than the low rate.

  The potential region where such gas G is generated varies depending on, for example, the type of additive, and the pressure of the wound body external space S is measured with a commercially available pressure sensor during the initial charging process. This is confirmed in advance based on the result of evaluating the potential region when the pressure increases.

In the manufacturing method, by performing the initial charging step in this way, the formation speed of the film is reduced, and the formation of the film catches up with the penetration of the electrolytic solution E into the central portion 100c in the axial direction of the wound body 100. Can be surely prevented. Moreover, the manufacturing method can fully permeate | transmit the electrolyte solution E to the axial direction center part 100c of the winding body 100. FIG.
Therefore, the manufacturing method can form a film on the entire surface of the wound body 100 after the electrolyte E has penetrated the entire surface of the wound body 100 during the initial charging step (or during high-temperature aging).

  That is, the manufacturing method can form a uniform film on the wound body 100 more reliably as compared with the case of charging at a high rate.

In the manufacturing method, it is preferable to charge at a rate of 1 C or less in a potential region where gas is generated. In particular, in the manufacturing method, it is particularly preferable to charge at a rate of 0.1 C or less.
Thereby, since the production method can make the gas generation more gradual, a uniform film can be more reliably formed on the wound body.

  Next, a description will be given of the results of manufacturing batteries by changing the type of additive added to the electrolytic solution E and evaluating the coating of each battery.

As shown in FIG. 11, in the evaluation of the film, the battery 10 of the present embodiment manufactured by adopting the additive LPFO of the present embodiment as an additive, and LiBOB (lithium bisoxalate borate, the structure shown below) A battery manufactured using the formula 2) was manufactured.

  The additive LiBOB is an additive in which the amount of gas generated by the decomposition reaction during film formation is less than that of the additive LPFO.

  Hereinafter, a battery manufactured using the additive LiBOB is referred to as a “battery of a comparative example”.

  In the evaluation of the film, each battery was manufactured under the same conditions except that the types of additives were different.

  In the evaluation of the film, after each battery was manufactured, the outer package 30 was disassembled, the wound body 100 was taken out, and the elements of the film formed on the wound body 100 were analyzed to evaluate the film.

In the battery of the comparative example, many elements of the film were detected from the middle in the axial direction of the wound body. Further, in the battery of the comparative example, the film element was not detected so much from the central portion in the axial direction of the wound body.
That is, in the battery of the comparative example, a uniform film was not formed on the wound body.

  This is considered to be due to the fact that the amount of gas generated by the decomposition reaction of the additive LiBOB during the initial charging step is small, so that the electrolyte solution could not penetrate to the central portion in the axial direction of the wound body. .

  On the other hand, as compared with the battery of the comparative example, the battery 10 of the present embodiment has a film uniformly formed from one axial end of the wound body 100 to the other axial end.

  Moreover, about the battery 10 which used LPFO as an additive with respect to the electrolyte solution E, and the battery which used LiBOB as an additive with respect to the electrolyte solution E, after injection | pouring of the electrolyte solution E in the exterior 30, at the time of completion | finish of high temperature aging Since the change with time of the internal pressure of the exterior 30 was confirmed, explanation will be given.

As shown in FIG. 12, after injecting the electrolytic solution into the exterior 30, when the exterior 30 is sealed and left, in both the additive LPFO battery 10 and the additive LiBOB battery, the electrolyte solution penetrates. The pressure inside the exterior 30 decreased.
Thereafter, when the initial charge is performed, in the additive LiBOB battery with a small amount of gas G generated, almost no change in the pressure in the exterior 30 was observed, but the additive LPFO battery 10 with a large amount of gas G generated. , The pressure inside the exterior 30 was restored to atmospheric pressure.

Furthermore, when high-temperature aging was started, the pressure in the exterior 30 increased due to an increase in battery temperature. In this case, in the battery of the additive LiBOB, the pressure inside the outer package 30 is lower than the saturated vapor pressure of the electrolytic solution E, and thus the electrolytic solution E continued to volatilize during high temperature aging. Thereby, the pressure in the exterior 30 continued to rise during high temperature aging.
On the other hand, in the battery 10 of the additive LPFO, the internal pressure of the exterior 30 increased to a value equal to or higher than the saturated vapor pressure of the electrolyte E as the battery 10 was heated. Therefore, volatilization of the electrolytic solution E did not occur during high temperature aging. As described above, in the battery 10 of the additive LPFO, the pressure inside the exterior 30 increased without volatilization of the electrolytic solution E, so that the penetration of the electrolytic solution E was promoted and the wound body 100 was uniformly wetted over the entire surface. .
Further, when the high temperature aging was completed, in the battery 10 of the additive LPFO, the pressure inside the exterior 30 decreased and returned to the atmospheric pressure. Also in the battery of additive LiBOB, the pressure in the exterior 30 decreased with the end of the high temperature aging.

  From the above, it can be seen that in the manufacturing method, it is preferable to add an additive that easily generates gas G (additive LPFO in the present embodiment) to the electrolytic solution E.

  Note that the manufacturing method is not limited to the additive LPFO as in the present embodiment as long as it is an additive that generates a large amount of gas in the decomposition reaction during film formation. For example, vinylidene carbonate can also be used as an additive that generates gas in the decomposition reaction during film formation.

10 Battery (secondary battery)
30 Exterior (battery case)
100 Winding body 100a / 100b Both ends in the axial direction E Electrolyte LPFO additive S Winding body outer space S1 Winding body inner space

Claims (5)

A method for producing a sealed secondary battery comprising a battery case, a wound body and an electrolyte,
Depressurizing the inside of the battery case in a state in which the wound body is housed so that the winding axis direction is parallel to the lower surface of the battery case;
Injecting an electrolytic solution to which an additive capable of generating a gas by a decomposition reaction is added into the decompressed battery case;
Sealing the battery case filled with the electrolytic solution;
Both ends of the wound body in the axial direction are on standby to reduce the differential pressure between the wound body outer space, which is a space between the battery case and the wound body, and the inner space of the wound body. Infiltrating the electrolyte solution from the portion to reduce the volume of the winding body internal space; and
A step of initially charging a secondary battery in which the electrolytic solution is infiltrated into the wound body;
Maintaining the sealed battery case while aging the initially charged secondary battery at a high temperature;
And
The electrolyte includes
Due to the generation of gas due to the decomposition reaction of the additive, an amount of additive is added such that the pressure in the battery case when performing the high-temperature aging step is higher than the saturated vapor pressure during high-temperature aging of the electrolyte. To be
A manufacturing method of a sealed secondary battery. The electrolyte includes
The amount of the gas is adjusted so that the pressure in the battery case when performing the high temperature aging step is higher than the saturated vapor pressure at the time of high temperature aging of the electrolyte by the generation of the gas,
In the initial charging step, an amount of the additive is added such that the pressure in the battery case is lower than the saturated vapor pressure during high-temperature aging of the electrolyte.
The manufacturing method of the secondary battery of Claim 1. The electrolyte includes
Due to the generation of the gas, the amount of the additive is added such that the pressure in the battery case at the end of the initial charge is approximately the same as the atmospheric pressure.
The manufacturing method of the secondary battery of Claim 1 or Claim 2. In the initial charging step,
In the potential region where the gas is generated, the secondary battery is charged at a lower rate than other potential regions.
The manufacturing method of the secondary battery as described in any one of Claims 1-3. A battery case ,
In the secondary battery of the previous SL and the wound body is parallel winding axis direction with respect to the lower surface of the battery case a wound body which is housed in the battery case, the hermetic equipped with an electrolytic solution, a There,
The front Symbol electrolyte, additives capable of generating gas by decomposition reactions are added,
The amount of the additive added is as follows:
By the generation of gas due to the decomposition reaction of the additive, sealed pressure in the battery case when performing Atsushi Ko aging is higher on the saturated vapor pressure at high temperature aging of the electrolyte;
A sealed secondary battery, characterized in that the amount satisfies the above .

Images